1. Technical Field
The disclosure relates to a technique of discrete cosine transformation (DCT), and more particularly to a discrete cosine transformation circuit for performing two-dimensional discrete cosine transformations.
2. Description of Related Art
DCT is known as a transformation method suitable for image data compression. Forward DCT is execution of DCT in the forward direction for transforming image data into frequency components, and an inverse DCT (IDCT) is execution of DCT in the backward direction for recovering the original image data by inversely transforming the frequency components. The term DCT can refer to either forward DCT, inverse DCT, or both forward and inverse DCTs.
Typically, a discrete cosine transform (DCT) apparatus performs a full two-dimensional (2D) transformation on a macroblock, for example, an 8×8 pixel block, by first performing a ID DCT on the rows of the 8×8 pixel block, then performing another 1D DCT on the columns of the 8×8 pixel block. Block-based transformations are widely utilized in different video coding standards, such as H.264, VC-1, and MPEG2, and may differ at least in their block sizes and coefficients. Dedicated DCT circuits may be designed for different video coding schemes. Integrating such dedicated circuits into one device makes the device supportive to multiple video coding schemes but may complicate circuit design and render circuit miniaturization more difficult. This is also inflexible when the device is required to accommodate new video coding schemes. Running different video coding schemes on a general-purpose processor is more flexible but inefficient.